This invention relates to a process for producing a cyanate ester resin cure product which comprises molding a cyanate ester resin composition to a desired shape at a temperature of not more than 50.degree. C., and preferably at room temperature to bring about primary curing, and then post-curing the resin molding at a temperature of not less than 170.degree. C. The cure products can be used for laminates, molded products, filament windings, coating materials, adhesives, cast products, and a variety of industrial uses.
It has been known that a polyfunctional cyanate ester compound can completely cured through forming of symtriazine ring by heating it in the presence or absence of an organic metal compound catalyst through forming of symtriazine ring. However, it was necessary to heat the cyanate ester compound at a temperature of not less than 150.degree. C. in the prior method using a conventional amount of catalyst.
Japanese Patent Publication (KOKOKU) No. 49-16800 discloses that the mixture of bisphenol A dicyanate (2 g) and methylene chloride (2 g) is heated in the presence of 1 mol % of salicylaldehyde cobalt [Co(Sal).sub.2 ] (metallic chelate catalyst) per the dicyanate at 25.degree. C. for 20 hours to form a polymer. However, if metallic chelate compounds or other organometallic salts are incorporated as catalysts in such amounts that primary curing is completed in about one or two days to become ready for post-curing, the time required for the mixture to become substantially nonflowable at a temperature of not more than 50.degree. C. is extremely shortened, less than several tens of minutes. Therefore, such metallic chelate compounds are unsuitable for use in practical applications. In addition, when the resin composition is used without using much solvent, the polymerization reaction is rapidly caused due to the reaction heat immediately after incorporating the catalyst into the resin composition and finally runaway reaction may occur; and in some case, there was a possibility that fire may be caused.
It was known that cyanato group (--O--C.dbd.N) of a polyfunctional cyanate ester compound reacts with an amino group, a hydroxy group, or carboxylate group at relatively low temperature. It was also known to prepare the cured resin by utilizing such properties of the polyfunctional cyanate ester compound. For example, Japanese Patent Publication (KOKOKU) Nos. 42-19458 and 44-1222 disclose that straight or network synthetic resins can be obtained through isourea ester group by blending a polyfunctional cyanate ester compound and a mono- or polyfunctional amine compound having cyanato groups and primary or secondary amine groups in stoichiometric amounts, respectively are blended, followed by reacting these group in the presence of a solvent. Japanese Patent Publication (KOKOKU) No. 44-4791 discloses that straight or network synthetic resins can be prepared through imido carbonate ester groups by blending a polyfunctional cyanate ester having cyanato groups and a polyvalent aliphatic acid or an aromatic hydroxy compound in stoichiometric amounts, followed by reacting them during heating in the presence of a solvent. However, when a substantial amount of these catalysts are used in these methods, the period when the substantially flowability of the resulting resin composition is lost is too short, as in the case of adding the above-mentioned metal compound to the system; and in addition runaway reaction tends to be caused. In order to solve such problems, a solvent must be used. In addition, linking groups of the resulting resin compositions contain active hydrogens and the imido carbonate ester groups start to heat-decompose at a temperature of about 150.degree. C.